Calculate voltage drop, receiving voltage, and wire loss for single-phase, three-phase, and DC circuits, then compare nearby AWG and kcmil sizes.
Estimate voltage drop (V), voltage drop (%), receiving-end voltage, and conductor loss for single-phase AC, three-phase AC, and DC circuits. Enter current, voltage, one-way length, conductor material, and wire size to compare the current setup against common 3% and 5% planning targets.
Enter one-way length in feet. The calculator automatically handles round-trip distance for single-phase and DC circuits.
This is a resistance-focused planning estimate. Long feeders, large motors, and reactive loads should still be checked against your project standard.
Enter positive values for voltage, current, one-way length, and wire size to update the results.
After you calculate, the drop percentage, receiving voltage, and suggested wire sizes will appear here.
This is the percentage drop relative to nominal voltage.
Estimated voltage at the load end.
Approximate I²R heat loss for the selected run.
The resistance summary will appear here.
| Wire size | Voltage drop | Voltage drop % | Receiving voltage | Status |
|---|---|---|---|---|
| Results will appear here after you calculate. | ||||
A voltage drop calculator estimates how much voltage is lost as current travels through a conductor. Enter the system type, nominal voltage, load current, one-way length, conductor material, and wire size to estimate receiving-end voltage, conductor loss, and whether the current wire size is close to common 3% or 5% planning targets.
This is especially useful for longer branch circuits, feeder runs, and low-voltage DC wiring where even a small voltage drop can affect motors, controls, lighting, or battery-powered equipment.
This tool is designed for quick planning checks before you open a full code table or project standard.
The calculator gives you more than a single number so you can make a faster planning decision.
Select the circuit type, then enter nominal voltage, load current, one-way length, conductor material, and wire size. For AC circuits, add a realistic power factor if you are checking a motor or another reactive load.
This tool uses 20°C conductor resistivity to estimate resistance. Copper uses 0.017241 Ω·mm²/m and aluminum uses 0.028264 Ω·mm²/m. Conductor resistance is estimated with R = ρ × L ÷ A, where L is one-way length converted from feet to meters and A is the nominal conductor area behind the selected AWG or kcmil label.
The planning formulas are simplified as DC: ΔV = 2 × I × ρ × L ÷ A, single-phase AC: ΔV ≈ 2 × I × ρ × L ÷ A × PF, and three-phase AC: ΔV ≈ √3 × I × ρ × L ÷ A × PF. These are fast planning formulas, not a full impedance model.
Many US designers use 3% and 5% as planning targets, but final design work still depends on your code path, equipment tolerance, temperature correction, conductor installation method, and any project-specific engineering standard.
Enter one-way length. The calculator automatically handles round-trip distance for single-phase AC and DC circuits, while the three-phase mode uses the common three-phase planning factor.
Power factor is an AC concept. DC mode always uses a power factor of 1 because reactive AC effects are not part of the model.
Aluminum has a higher resistivity than copper, so the same run length and the same cross-sectional area will usually produce a larger voltage drop and more conductor loss.
Treat them as planning targets, not automatic approval. Many branch-circuit discussions use 3% and many whole-run discussions use 5%, but your final check should still match the applicable code and project standard.
No. Use it for planning and quick comparisons, then confirm the final result with the relevant code tables, temperature correction, conductor installation method, and any required engineering review.
Code tables and manufacturer data may include additional impedance effects, temperature assumptions, conductor construction differences, or installation conditions that a fast planning calculator does not model.
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